Extrusion mill



1944- E. T. MEAKIN 2,354,924

'EXTRUSION MILL Filed Jan; '15, 1941 IN VEN TOR. EDGAR 7'. MEAK/N.

A 7' TOENEY Patented Aug. 1, 1944 UNITED s'rA'rEs PATENT ,orncsax'rausron mu.

Edgar 'r. Mcakin, San Francisco, Calif. Application January 15, 1941,Serial No. 314,447 4 Claims. (01. 76-107) My invention relates toextrusion mills, and more particularly to a die structure for use insuch mills.

The extrusion mill to which my invention in particular pertains, is ofthat type employed for the consolidation of meal, mashes, chemicals andthe like, into pellet form. Such mill includes as its main components, adie I and an extrusion element such as a roller I, operativelyassociated therewith. The material to be consolidated is introduced uponthe compression surface of. the

die, and upon initiatingrelative movement between the die I and theextrusion element 3, the material is forced through die apertures orholes I, to emerge in the form of strings or rods of consolidatedmaterial from which the pellets are formed by severance.

It has been the general practice in the past to manufacture the dieswith the die holes normal to the compression surface of the die, and insome cases, to bevel or countersink the compression end of such holes tofacilitate entrance of material therein. A countersink tool preferablyemployed, isone tapered to an angle of about 60. It has been foundpossible to increase the capacity of a die of this type by slanting thedie holes, preferably to an angle of the order of 18 to theperpendicular, in accordance with the disclosure of the patent to EdgarN. Meakin, No. 2,171,039, of August 29, 1939. The die holes of thispatent, accordingly, also lie at an acute angle to the compressionsurface of the die. In either of the above types, where countersinkinghas been employed, the countersink has been formed in the natural andcustomary manner by applying the countersinking tool centrally of thecompression end of the die hole, and countersinking normal to the diesurface. The effect of this is to produce a bevel around the entireperiphery of the compression end of the die hole.

Among the objects of my invention are- (I) To increase the normal outputof extrusion mills,

(2) To increase the output of extrusion mills through a slightmodification of the die structure thereof and without necessitating theaddition of extra parts to the mill structure,

(3) To provide an improved die which will require less power in theextrusion of material therethrough, and thus bring about an increase inthe output of the mill, and

' (4) To provide an improved method of forming a die to increase itsefficiency by reducing its resistance to extrusion of materialtherethrough.

Additional objects of my invention will be brought out in the followingdescription of the same taken in conjunction with the accompanyingdrawing wherein Figures 1, 2 and 3 illustrate three embodiments of myinvention as applied to die holes which are normal to the compressionsurface of the die,

Figures 4, 5 and 6 illustrate corresponding embodiments as applied todies incorporating slanting holes, and

Figure '7 is a fragmentary view of a cylindrical die and associatedroller, incorporating holes of the type depicted in Figure 6 and bearingdescriptive legends.

I have discovered that die holes formed with a countersink in accordancewith prior art practice, have certain limiting characteristics in thematter of extruding material therethrough, and this I attribute to theexistence of the slope formed at the trailing edge 9 of the compressionend of the die hole. As I analyze what takes place during a compressioncycle, a good percentage of the material which should be passing throughthe die hole is permitted to slide out of the die hole by way of thesloping trailing edge of the countersink, during the early approach ofthe die hole toward the extrusion member in the compression cycle. Thisrepresents a waste of energy which produces no useful result in so faras extruding material through the die hole is involved, and serves tocut down the efliciency of the die.

Another factor which I believe is involved, takes eifect as the die holeapproaches closer to the extrusion member, because when the slopingtrailing edge presents a surface normal to the compression force of theextrusion roller, which it must do at some point in the compressioncycle, the material will be compacted against this same sloping surfaceof the countersink, which is equivalent to pre-compaction and serves nouseful purpose in extruding the material through the die hole.Followingits pre-compaction in this, manner, the material, in itscompacted condition, must then be caused to change its direction ofmovement as the die hole approaches closer to the extrusion roller, allof which represents wasted energy, resulting in a further lowering. ofthe efliciency of the die member.

I have found that, without changing the countersink tool, the efficiencyof a die may be increased to a surprising degree by so countersinkingthe die holes as to leave no appreciable slope at the trailing edge 9 ofthe compression end of the die hole. One way of accomplishing this, asdepicted in Figures 1 and 4, is to cause the countersinking tool H toapproach the die hole I toward the center II of the compression endthereof in a direction against the intended relative movement of the dieat an acute angle to the compression surface I of the die. This willenable the tool to countersink the leading edge I! of the entrance tothe hole, without engaging the trailing edge I, though, in practice, Iprefer to countersink to the point where the tool will just about takethe sharpness of! the trailing edge. This is done primarily as aprecaution against chipping, particularly in the event some hard foreignmaterial should accidentally find its way into the mill.

Another manner of accomplishing this result depicted in Figures 2 and 5,is to locate the center I! of countersink eccentric with respect to thecenter II of the die opening in the compression surface of the die, andin the direction of intended relative movement of the die member. Bythusly locating the center of countersink, the tool I I may be operatedin a direction normal to the compression surface I of the die, and asubstantial countersinking of the hole may be obtained before thecountersinking tool reaches the trailing edge 9 of the die hole. Thismethod is preferred for use with holes which are normal to thecompression surface ofthe die, as in Figure 2, in which case, the axis II of countersink will be parallel to the axis 2| of the die hole.

As for dies in which the holes slant with respect to the compressionsurface, I prefer a combination of the methods lust discussed, that is,to locate the center II of the countersink eccentric to the center ll ofthe compression end of the die hole, and in the direction of theintended relative movement of the die, and then cause the tool II toapproach the compression surface 5 at an acute angle to the compressionsurface, as depicted in Figure 6. The acute angle'is preferably the sameas that which the hole proper makes with the compression surface, inwhich case, the axis ll of countersink will parallel that of the hole.Thus, in both preferred forms, the same parallel relationship will existbetween the hole axis 2| and the countersink axis It.

The offset center I! and angular approach depicted in Figure 6 can alsobe applied to holes which are normal to the compression surface. This isillustrated in Figure 3, though this is not the preferred way ofcountersinking holes of this character.

In each of the above cases, I prefer to smooth oi! the sharpness of thetrailing edge 9 of the compression end of each hole for the purposepreviously indicated. Such smoothing oi! of the edge in question is notto be considered as essential to the improved countersink of myinvention and the method of forming the same.

when the die hole is constructed in accordance with any of the abovemethods, leaving the trail ing edge 9 of the compression end of the holesubstantially free of any bevel or slope, practically none of thematerial which enters the countersink can be forced out over thetrailing edge during the compression cycle, and must, therefore, enterinto the hole proper, to which it was initially directed.

At the same time, my improved method of countersinking has the effect ofstreamlining the countersink, thereby enabling the material to be guidedinto the die hole proper with less resistance to its movement and,accordingly. less pre-compaction.

The application of my invention to holes of the slanting type, such asdisclosed in the aforementioned Meakin patent, has brought aboutsurprising results, .as compared to the output obtained from a similardie in which the countersinks were formed in the customary manner, thatis, normal to the compression surface of the die, as illustrated in thedrawings in the aforementioned Meakin patent. Whereas, with a dieconstructed in accordance with this Meakin patent, I have been able toobtain an output of the order of 17 bags per hour; with a correspondingdie countersunk in accordance with my present invention, I have beenable to increase the output of the same mill to from 50 to 60 bags perhour, representing an increase of the order of 300%-350%, accompanied bya. very material decrease in power consumption.

My invention is not limited to die holes of circular cross section, butis applicable to holes of any cross-sectional configuration andregardless of whether the countersinking is to be accomplished with aconical countersink tool or by beveling the edges of the hole.

While I have disclosed my invention in detail, the same is subject tovariation and modification, without departing from the principlesthereof, and I accordingly do not desire to be limited in my protectionto the details set forth, except as may be required by the prior art andthe appended claims.

I claim:

1. The method of forming a die hole in a die comprising a compressionsurface for use in an extrusion mill, wherein there is relative movementbetween said die and an extrusion element cooperatively disposed withrespect to the compression surface of said die, the extreme limits ofthe hole in the direction of movement of the element being defined by aleading edge and trailing edge respectively, comprising, forming a holethrough said die, countersinking the material bounding said hole byrotating a tool provided with a cutting edge about an axis eccentric ofthe axis of the hole, said tool having a radius greater than the radiusof the hole and the locus of the cutting edge of the tool issubstantially tangential to the mid-portion of the trailing edge of thehole, whereby the material adjacent the mid-portion of the trailing edgeis removed.

2. A method according to claim 1, wherein the axis of the tool isparallel to the axis of the die hole.

3. A method according to claim 1, wherein the axis of the toolintersects the axis of the die hole.

4. A die for a pellet mill wherein an extrusion element is caused tomove over a die, said die comprising a compression surface and having anextruding hole therethrough, the material of said die defining the endof said hole adjacent the compression surface terminating in acountersink, said countersink substantially encompassing the hole andbeing tangential to the hole at only the trailing edge thereof.

EDGAR T. MEAKIN.

